Retinal Vessel Tortuosity in Infants at Risk for Retinopathy of Prematurity Between 31 and 34 Weeks Post-Menstrual Age

Abstract

Purpose: : To compare early retinal vascular tortuosity of subjects that develop Type 1 retinopathy of prematurity (ROP) requiring treatment with controls with no ROP or ROP less than Type 1.

Methods: : Digital fundus imaging was performed using a Nidek NM200D non-contact camera between 31 and 34 weeks post-menstrual age (PMA). Fundus photographs were masked and assessed using ROPnet semi-automated software (Fiorin and Ruggeri, University of Padua) which traces retinal vessels and estimates tortuosity in arbitrary units (AU). Tortuosity was measured for the major superior and inferior retinal arteries and veins. 56 right eyes from infants at risk for ROP (weight ≤1251g and PMA <30 weeks) were included. Retinal vessels of eyes that developed Type 1 ROP requiring treatment were compared with controls.

Results: : 11 infants developed Type 1 ROP requiring treatment. Average PMA at the time of fundus photography was 33 weeks for both treated and control eyes. Grade-regrade comparisons showed no statistically significant differences. On average, the group of eyes that developed Type 1 ROP requiring treatment had significantly more tortuous vessels than control eyes for the superior artery (mean 0.85 AU vs 0 AU, p =0.001). No statistically significant differences were observed for inferior artery (0 AU vs 0 AU, p =0.51), superior vein (0 vs 0.05, p=0.23) or inferior vein (0 vs 0, p=0.84). The majority of subjects at this premature age had minimal tortuosity. An arbitrary threshold of 1.5 AU was chosen as a value above which tortuosity was considered very high. Of the subjects that later developed Type I ROP, 30% had high arterial tortuosity values ≥ 1.5 (p=0.009), whereas none in the control group had such values.

Conclusions: : The analysis presented here shows that at 31-34 weeks PMA the majority of subjects in both groups had small tortuosity values. Although retinal arterial tortuousity measurements were not large at this early stage of development, the results suggest that the values obtained for the superior arteries may help identify high-risk infants. In general, subjects who had large arterial tortuosity were more likely to need treatment in the future. More research is needed on a larger sample size to elucidate the role of tortuosity measurements in the identification of infants at risk for Type 1 ROP.

Keywords: retina • retinopathy of prematurity • laser